1. Field of the Invention
The present invention relates to an art to detect fine contaminant particles/defects on a thin film substrate, a semiconductor substrate, a photomask and the like, if present. The present invention relates particularly to an art to improve detection sensitivity of the fine contaminant particles/defects.
2. Background Art
In a production line of the semiconductor substrate, thin film substrate and the like, inspection of a contaminant particle adhering to the surface of the semiconductor substrate, thin film substrate and the like is conducted in order to monitor dusting situation of a manufacturing device. For example, in the case of the semiconductor substrate before a circuit pattern is formed, a fine contaminant particle or defect with a size of several tens nm or less should be detected on the surface. As an art to detect the fine defects on the surface of an article to be inspected such as a semiconductor substrate and the like, as described in U.S. Pat. No. 5,798,829, for example, there is a prior art in which a focused laser light flux is fixedly irradiated onto the semiconductor substrate surface (an irradiated region formed by the irradiated laser light flux on the semiconductor substrate surface at this time is referred to as an illumination spot), a scattered light from the contaminant particle generated when the contaminant particle adhere onto the semiconductor substrate is detected, and the contaminant particle or defect on the entire surface of the semiconductor substrate are inspected by rotation and translational feeding of the semiconductor substrate. An ellipsoidal mirror is used for detection of the scattered light, and by setting a detection position on the semiconductor substrate at a primary ellipsoidal focal point and arranging a photosensitive surface of a photosensitive element at a secondary focal point, the scattered light generated in the contaminant particle can be focused with a wide solid angle so that the fine contaminant particle can be detected. As the laser light flux in plural for illuminating the semiconductor substrate in this prior art, only one flux corresponds to a single incident angle, and there is only one illumination spot formed on the semiconductor substrate surface by the laser light flux.
As another prior art, as described in JP Patent Publication (Kokai) No. 2001-255578, for example, condenser lenses and photodetectors are arranged at positions where a plurality of elevation angles and a plurality of azimuthal angles are combined with respect to the semiconductor substrate surface, and by detecting the scattered light focused by each of the condenser lenses by the photodetectors, detection in an advantageous direction is made possible according to a three-dimensional radiation distribution characteristics of the scattered light from the fine contaminant particle. In this prior art, too, two laser light fluxes of oblique illumination and normal illumination are provided for illuminating the semiconductor substrate, but there is only one laser light flux which corresponds to a single incident angle, and there is only one illumination spot formed by the laser light flux on the semiconductor substrate surface.